Beryllium hydride compositions and their use in making cyclopentadienyl beryllium hydride compounds

ABSTRACT

BERYLLIUM HYDRIDE, DISSOLVED IN A NOVEL SOLVENT THEREFOR, DICYCLOPENTADIENYL BERYLLIUM, REACTS WITH THE LATTER ON PROLONGED HEATING AT 105-115$ C. TO YIELD CYCLOPENTADIENYL BERYLLIUM HYDRIDE. THIS COMPOUND IS USEFUL AS AN INTERMEDIATE FOR CYCLOPENTADIENYL BERYLLIUM ALKYLS AND AS THE BASIS OF A LOW-PRESSURE ROUTE TO CRYSTALLINE BERYLLIUM HYDRIDE.

3,755,479 BERYLLIUM HYDE COMPOSITIONS AND THEIR USE IN MAKINGCYCLOPENTADI- ENYL BERYLLIUM HYDRIDE COMPOUNDS Everett M. Marlett andRobert N. Sanders, Baton Rouge, La., assignors to Ethyl Corporation,Richmond, Va. No Drawing. Filed Oct. 24, 1967, Ser. No. 678,489 Int. Cl.C07f 3/00 US. Cl. 260-665 R 6 Claims ABSTRACT OF THE DISCLOSUREBeryllium hydride, dissolved in a novel solvent therefor,dicyclopentadienyl beryllium, reacts with the latter on prolongedheating at 105-115 C. to yield cyclopentadienyl beryllium hydride. Thiscompound is useful as an intermediate for cyclopentadienyl berylliumalkyls and as the basis of a low-pressure route to crystalline berylliumhydride.

This invention relates to and has as its principal ob jects theprovision of a novel solvent for beryllium hydride, the provision of theresulting solution and the provision of a novel method for thepreparation of cyclopentadienyl beryllium hydride from said solution.

In accordance with the present invention it has been found that whendicyclopentadienyl beryllium or a bis (monoor dialkyl cyclopentadienyl)beryllium, wherein each alkyl group may contain up to about 8 carbonatoms, is mixed with beryllium hydride and the mixture is heated to atemperature of 60 to 90 C. for a period of one-half hour to about 10hours, the beryllium hydride dissolves in the cyclopentadienyl berylliumcompound to form a solution stable at ambient temperature. This solutionand the foregoing process for its preparation constitute embodiments ofthe present invention.

Furthermore, it has been found that when the solution prepared asdescribed above is heated to a reaction temperature in the range of fromabout 105 to about 115 C. under a reduced pressure of from about 0.01millimeter of mercury to about 1 atmosphere for a period of from about 6to about 48 hours, a homogeneous liquid product is obtained whichcontains a simple or substituted cyclopentadienyl beryllium hydride andfrom which said hydride can be separated by known procedures. Thisprocess likewise constitutes an embodiment of the present invention.

Moreover, it has been found in accordance with this invention that asimple or substituted cyclopentadienyl beryllium hydride can be preparedby a two-stage process wherein the first stage comprises the preparationof a solution of beryllium hydride in a simple or substituteddicyclopentadienyl beryllium as described above and the second stagecomprises the chemical conversion of said solution to a liquid productcontaining a simple or substituted cyclopentadienyl beryllium hydridefollowed by the separation of said hydride from said liquid product byknown methods. The foregoing two-stage process is a preferred embodimentof the present invention.

The preparation of unsubstituted cyclopentadienyl beryllium hydride bythe foregoing two-stage process is also a preferred embodiment of thepresent invention. Other embodiments will appear hereinafter.

The process of the present invention offers an important advantage overprocesses hitherto available for the preparation of organoberylliumcompounds from beryllium hydride. Beryllium hydride, like many othermetallic hydrides, is a polymeric material which because of its highmolecular weight is relatively inactive chemically and which must beheated to depolymerization temperature (with consequent danger ofthermal decomposition, at least in part, of the beryllium hydride8,755,479 Patented Aug. 28, 1973 monomer) before olefination will occur.Presumably if the beryllium hydride were in solution it would be presentin a monomeric or other low molecular weight form and consequently wouldbe more reactive at lower temperatures. Unfortunately, few if anysolvents have been reported for beryllium hydride. The above-disclosedand wholly unexpected solvent power of dicyclopentadienyl berylliumcompounds for beryllium hydride is an important advantage of the presentinvention. The resulting solution is stable and, as indicated above, isa useful raw material for the preparation of cyclopentadienyl berylliumhydride. It is remarkable in that both solvent and solute are berylliumcompounds, and both are of interest as potential components of rocketfuels.

EXAMPLE I Preparation of dicyclopentadienyl beryllium Into a290-milliliter ball mill with one-quarter-inch stainless steel ballswere introduced 2.88 grams of beryllium chloride, 12.68 grams ofcyclopentadienyl sodium and milliliters of anhydrous diethyl ether. Thesystem was ball-milled overnight.

The mill contents were filtered through a medium-frit filter using ahelium back pressure. The filtrate was sealed in a flask and cooled witha Dry Ice-acetone eutectic. After an hour the ether was distilled toabout half its initial volume and the system again cooled. A solidformed in the flask; it was filtered and dried.

The product was sublimed at 40 to 45 C. under an absolute pressure of0.09 millimeter of mercury, the resulting crystals being collected andweighed in a dry box. The clear white crystals weighed 0.34 gramcorresponding to a yield of 6.8 percent on beryllium chloride. An X-raypowder pattern showed the product to be highpurity crystallinedicyclopentadienyl beryllium.

When the process of Example 1 is repeated, except for the replacement ofthe cyclopentadienyl sodium with methyl cyclopentadienyl sodium, ethylcyclopentadienyl sodium, n-propyl cyclopentadienyl sodium, isopropylcyclopentadienyl sodium, n butyl cyclopentadienyl sodium, isobutylcyclopentadienyl sodium, tertiary butyl cyclopentadienyl sodium, n-hexylcyclopentadienyl sodium, n-octyl cyclopentadienyl sodium, isooctylcyclopentadienyl sodium, dimethyl cyclopentadienyl sodium, diethylcyclopentadienyl sodium, methylethyl cyclopentadienyl sodium, ormixtures of the foregoing, similar results are obtained.

When the process of Example 1 is repeated except for the replacement ofthe cyclopentadienyl sodium with cyclopentadienyl lithium,cyclopentadienyl potassium, cyclopentadienyl rubidium orcyclopentadienyl cesium or mixtures thereof, similar results areobtained.

When the beryllium chloride of Example 1 is replaced with berylliumbromide, beryllium iodide, or mixtures thereof, the other reactionconditions remaining unchanged, similar results are obtained.

EXAMPLE 2 Preparation of cyclopentadienyl beryllium hydrideDicyclopentadienyl beryllium (0.170 gram) and 0.013 gram of 96.7 percentpurity beryllium hydride were placed in a glass ampoule which was sealedand heated at 65 C. for 4 /2 hours. A liquid product was obtained whichsolidified between 49 and 50 C. (pure dicyclopentadienyl beryllium meltsat 60 C.). The mixture was then heated for 24 hours at 80 C. with nochange in the properties of the product. However, when the temperaturewas raised to C. for 24 hours, a colorless liquid was obtained which hada freezing point between 5 and 6 C. The density of the liquid wasapproximately 0.64 gram per cubic centimeter. This liquid wastransferred to a micro vacuum distillation apparatus which was designedto allow the distillate to condense partially at room temperature, andthen to pass the uncondensed vapor into a receiver cooled in liquidnitrogen. The liquid was vacuum distilled at 0.04 millimeter while thesample was heated to a final pot temperature of 75 C. All the liquid inthe pot was vaporized. White solid (about 1 milligram) was found in theliquid nitrogen-cooled receiver. Infrared analysis of the productrevealed only berylliumhydrogen bridge bonds. The material collected inthe room temperature portion of the condenser was subjected to X-rayanalysis and was found to have a powder pattern identical to that ofdicyclopentadienyl beryllium.

From the above it is evident that the liquid of freezing point 5 to 6 C.w as cyclopentadienyl beryllium hydride which decomposed upondistillation to beryllium hydride and dicyclopentadienyl beryllium.

When the above liquid of freezing point 5 to 6 C. is subjected tocareful low-temperature distillation in a molecular still,cyclopentadienyl beryllium hydride of a high degree of purity isobtained.

When the above liquid is prepared from a mixture containing a slightexcess of beryllium hyride and is extracted at low temperature withpetroleum naphtha and the solvent is evaporated from the extract at lowtemperature and pressure, cyclopentadienyl beryllium hydride isobtained.

When the process of Example 2 is repeated except for the replacement ofthe dicyclopentadienyl beryllium with bis(methylcyclopentadienyl)beryllium, bis(ethylcyclopentadienyl) beryllium, bis(propylcyclopentadienyl) beryllium, bis(isopropyl cyclopentadienyl)beryllium, bis (n-butyl cyclopentadienyl) beryllium, bis(isobutylcyclopentadienyl) beryllium, bis(tetriary butyl cyclopentadienyl)beryllium, bis(n-hexyl cyclopentadienyl) beryllium, bis(n octylcyclopentadienyl) beryllium, bis (isooctylcyclopentadienyl) beryllium,bis(dimethyl cyclopentadienyl) beryllium, bis(diethyl cyclopentadienyl)beryllium, bis(methylethyl cyclopentadienyl) beryllium, or mixtures ofthe foregoing, similar results are obtained.

For the sake of clarity in discussing reaction conditions, the twostages, disclosed above, of the reaction of the invention will bediscussed separately. The preparation of the solution of berylliumhydride in the cyclopentadienyl beryllium compound will be referred toas the solution stage and the preparation of the cyclopentadienylberyllium hydride from this solution as the reaction stage.

The solution stage.As indicated above, a wide variety of simple andsubstituted cyclopentadienyl beryllium compounds can be employed assolvents for beryllium hydride. In addition to those listed above, thefollowing cyclopentadienyl beryllium compounds may be employed:bis(di-npropyl cyclopentadienyl) beryllium, bis(di-n-butylcyclopentadienyl) beryllium, bis(diisobutyl cyclopentadienyl) beryllium,bis(diisohexyl cyclopentadienyl) beryllium, bis (di-n-octylcyclopentadienyl) beryllium, bis (methylpropyl cyclopentadienyl)beryllium, bis(methylisopropyl cyclopentadienyl) beryllium, bis(n-butylcyclopentadienyl) beryllium, bis(isobutyl methylcyclopentadienyl)beryllium, bis(ethylpropyl cyclopentadienyl) beryllium,bis(ethylisopropyl cyclopentadienyl) beryllium, bis(ethyl n-butylcyclopentadienyl) beryllium, bis(ethylisobutyl cyclopentadienyl)beryllium, bis(ethyl-n-pentyl cyclopentadienyl) beryllium,bis(ethylisohexyl cyclopentadienyl) beryllium, bis(n-propyl n octylcyclopentadienyl) ber llium, bis (methyl-n-heptyl cyclopentadienyl)beryllium, and mixtures thereof.

The molar ratio of beryllium hydride to the cyclopentadienyl berylliumcompound in the above solution can vary from 0.01 or less to 2.0 or moredepending upon the solubility of the beryllium hydride in the particularcyclopentadienyl compound employed. In general, equimolar proportionsare preferred because of the simplicity of the subsequent reaction andthe relative ease of separating the resulting cyclopentadienyl berylliumhydride compound from the reaction mixture.

The solution temperature can range from 40 C. or below to 100 C. orabove, but temperatures, in the range of 60 to C. are preferred. Attemperatures below 60 C. solution proceeds so slowly as to beimpractical whereas at temperatures above 90 C. conversion to thecyclopentadienyl beryllium hydride compound may begin before solution iscomplete, with a resultant reduction in yield.

The dissolution of the beryllium hydride can be carried out underpressures varying from 0.01 millimeter of mercury or less to 1atmosphere or more. For ease of manipulation and because of the relativesimplicity of the required apparatus, pressures in the neighborhood of 1atmosphere are preferred.

The dissolution of the beryllium hydride will require from half an houror less to 10 hours or more depending upon the particularcyclopentadienyl beryllium compound employed if desired. Suitablecosolvents are benzenes, beryllium hydride. For high-purity finelydivided beryllium hydride and unsubstituted dicyclopentadienylberyllium, solution periods of 2 to 5 hours are adequate and aretherefore preferred.

Solvents other than the cyclopentadienyl beryllium compound areunnecessary in the solution stage but may be employed if desired.Suitable cosolvents are benzenes, toluene, cyclohexane andcyclopentadiene. When the cyclopentadienyl beryllium hydride compound isto be employed as an intermediate it can be prepared in a solvent andused without separation therefrom.

The reaction stage.In the second or reaction stage, the solution fromthe first stage is heated at reaction temperature for a period longenough to bring about essentially complete reaction with the formationof the cyclopentadienyl beryllium hydride compound. Reactiontemperatures can range from or less to 130 C. or more depending upon theother reaction conditions. For the synthesis of the unsubstitutedcyclopentadienyl beryllium hydride, temperatures in the range of to C.are preferred because under these conditions the reaction goes tocompletion in a reasonable time and relatively high yield of the productcan be obtained.

Reaction pressures can range from less than 0.01 to more than 1atmosphere but atmospheric pressure is preferred for the reasons givenabove.

Under the foregoing reaction conditions, reaction is essentiallycomplete in 6 to 48 hours, depending upon the particular conditionsemployed.

All of the foregoing reactions must of necessity be carried out under anatmosphere inert with respect to both reactants and products. Suitableatmospheres include dry nitrogen, hydrogen, helium, neon, argon,krypton, xenon and those saturated aliphatic hydrocarbons which aregaseous under the reaction conditions. Mixtures of the foregoing inertgases are also satisfactory.

The cyclopentadienyl beryllium hydride compounds prepared by the processof this invention are useful intermediates for the preparation byolefination of cyclopentadienyl beryllium alkyl compounds. They are alsoof great interest as the basis of a low-pressure route for thepreparation of crystalline beryllium hydride and as high-energy liquidrocket fuels. Further applications include their use as terminatinggroups for other liquid beryllium hydride compositions of high hydrogencontent, e.g.,

CpBeH (BeH HBeCp (wherein Cp represents the cyclopentadienyl group), andas components of homogeneous polymerization catalysts.

We claim:

1. Two-stage process for the preparation of a cyclopentadienyl berylliumhydride compound which comprises, in the first stage, mixing berylliumhydride with a dicyclopentadienyl beryllium compound in a molar ratio offrom about 0.01 to 1 to about 2 to 1 and heating the mixture at asolution temperature of from about 40 to about 100 C. for a period offrom about one-half hour to about hours and under a pressure of fromabout 0.01 millimeter of mercury to about 1 atmosphere to produce asolution of beryllium h'ydride in said dicyclo pentadienyl berylliumcompound and, in the second stage, heating said solution at a reactiontemperature of from about 100 to about 130 C. and under a pressure offrom about 0.01 to about 1 atmosphere for a period of from about 6 toabout 48 hours to produce a reaction mixture containing acyclopentadienyl beryllium hydride compound and separating saidcyclopentadienyl beryllium hydride compound from said reaction mixture,all operations being carried out under an atmosphere of inert gas.

2. The process of claim 1 wherein said cyclopentadienyl berylliumhydride compound is unsubstituted cyclopentadienyl beryllium hydride andwherein said dicyclopentadienyl beryllium compound is unsubstituteddicyclopentadienyl beryllium.

3. The process of claim 1 wherein said solution temperature is fromabout to about C. and wherein said reaction temperature is from about105 to about 115 C.

4. Process for the preparation of a cyclopentadienyl ber'yllium hydridecompound which comprises heating a solution of beryllium hydride in adicyclopentadienyl beryllium compound, wherein the molar ratio of beryllium hydride to dicyclopentadienyl beryllium compound is from about 0.01to 1 to about 2 to 1, at a temperature of from about to about 130 C. fora period of from about 6 to about 48 hours to produce a reaction mixturecontaining a cyclopentadienyl beryllium hydride compound, and separatingsaid cyclopentadienyl beryllium hydride compound from said reactionmixture, all operations being carried out under an atmosphere of inertgas.

5. The process of claim 4 wherein said cyclopentadienyl berylliumhydride compound is unsubstituted cyclopentadienyl beryllium hydride andwherein said dicyclopentadienyl beryllium compound is unsubstituteddicyclopentadieneyl beryllium.

6. The process of claim 4 wherein said temperature is is from about toabout C.

Coates et al., Organometallic Compounds, vol. I, Methuen & Co. Ltd.,London, 1967, pp. 109 and 119 (QD 411 O6).

LELAND A. SEBASTIAN, Primary Examiner US. 01. X.R.

mg? 1 v UNITED STATES PATENT owner;

CERTIFICATE OF CCRRECTHN Patent No. 3,755,479 1' Dated Aug 2 1973Inventor(s)' Everett M. Marlett and Robert N. Senders It is certifiedthat error appears in the ebove-identified patent and' that saidLett'ersPatent are hereby corrected as shown below:

Column 5, line 14', "5 to 6C, w as" should read 5 to 6C. was Column 4,lines 18-19, "employed if desired. Suitable cosolvents are benzenes,beryllium hydride. For high-purity finely divided bery1-" should reademployed and upon the purity and particle size of the beryllium hydride,For high-purity. finely divided beryl- Signed and sealed this 18th dayof December- 1973.

(SEAL) Attest:

EDWARD M. FLETCHER, JR. RENE D, TEGTD [EYER V Attesting Officer I ActingCommissioner of Patents (5/69) UNITED STATES PATENT OFFICE CERTEFECATE0F CQRREQTEQN Patent No. Dated August 2 1973 Inventor(s)' Everett M.Marlett and Robert N. Sanders It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 3, line 14', "5 to 6C. w as" should read 5 to 6C. was Column 4,lines 18-19, "employed if desired. Suitable cosolvents are benzenes,beryllium hydride. For high-purity finely divided berylshould reademployed and upon the purity and particle size of the beryllium hydride.For high-purity finely, divided beryl- Signed and sealed this 18th dayof December 1973.

(SEAL) Attest:

EDWARD M. FLETCHER, Attesting Officer RENE D TEGTMEJYER ActingCommissioner of Patents

